Add ui_LifebarOnlyDamaged toggle to hide full-HP lifebars

[M3RT1N99]

Summary

• Adds a new ConVar ui_LifebarOnlyDamaged. When set to 1, lifebars only appear once a unit takes damage; full-HP units skip the lifebar batch entirely. Default 0 (vanilla behaviour).
• Mirrors Warcraft 3's "Show Lifebars Only When Damaged" option.
• Provides a noticeable FPS gain in dense crowds where most units are undamaged, since the per-frame lifebar batching cost scales with the unit count.

https://discord.com/channels/197033481883222026/1492294267492634674

Companion PR

The matching settings UI option lives in FAForever/fa#7085 — adds a HUD toggle that drives this ConVar via ConExecute. The two PRs should land together: this binary patch alone makes the ConVar available in the in-game console, the Lua PR alone is a no-op without this patch.

How it works

Hooks the call sub_85EED0 at 0x85C09F inside Moho::CWldSession::RenderStrategicIcons (the lifebar enqueue inside the per-unit loop). The 5-byte CALL is replaced with call LifebarFilter (same encoding length, no padding).

LifebarFilter is a small asm filter that:

1. Saves caller state with pushad

2. Reads the ui_LifebarOnlyDamaged flag — if 0, falls through to the original

3. Reads the same HP fields the actual lifebar drawing function sub_85CD40 uses for the bar fill fraction:

   v18 = *(float **)eax0;        // entry[0] -> unit data ptr
   v19 = v18[26] / v18[27];      // current HP / max HP

   So we dereference entry[0] and read offsets 104 / 108 from the unit data pointer.

4. If current HP < max HP → tail-calls sub_85EED0 (render)

5. If current HP >= max HP → returns without enqueueing (suppress)

The custom calling convention of sub_85EED0 (eax = lifebar entry buffer pointer, ecx = batch vec pointer) is preserved on both paths via pushad/popad.

Files

• hooks/LifebarFilter.hook — 5-byte CALL replacement at 0x85C09F
• section/LifebarFilter.cpp — ConVar registration + asm filter
• changelog.md — entry under Additions
• Info.txt — documents sub_85EED0, sub_85CD40, and the entry HP layout

Test plan

• Spawn many full-HP units in sandbox, enable ui_LifebarOnlyDamaged 1 — verify lifebars disappear for all of them
• Damage a unit — verify its lifebar appears immediately
• Heal it back to full HP — verify lifebar disappears again
• Set ui_LifebarOnlyDamaged 0 — verify all lifebars come back (vanilla behaviour)
• Verify no crash on unit death / unit creation while filter is active

🤖 Generated with Claude Code

[coderabbitai]

📝 Walkthrough

Walkthrough

These changes implement a "show lifebars only when damaged" feature controlled by a new ui_LifebarOnlyDamaged ConVar. When enabled, lifebars display exclusively for units not at full health. Implementation spans documentation, hook registration at address 0x0085C09F, and inline x86 assembly that conditionally suppresses lifebar rendering based on unit health status.

Changes

Cohort / File(s)	Summary
Documentation Info.txt, changelog.md	Added descriptive comments documenting the lifebar filter patch, its function addresses, and the new ConVar's behavior.
Lifebar Filter Hook & Implementation hooks/LifebarFilter.hook, section/LifebarFilter.cpp	Registered hook at 0x0085C09F to intercept RenderStrategicIcons calls. Implemented LifebarFilter function with x86 assembly that checks unit current HP against max HP; renders lifebars only when unit is damaged. Exposed ui_LifebarOnlyDamaged ConVar (backed by g_LifebarOnlyDamaged global) to control filter behavior.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A filter most clever, with asm so fine,
Lifebars appear when damage draws a line,
Register-saved hops through conditional streams,
Only the wounded show health on our screens! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding a UI toggle to hide lifebars for units at full health.
Linked Issues check	✅ Passed	The PR does not reference any linked issues, but the description is self-contained and the objectives are clear without external issue context.
Out of Scope Changes check	✅ Passed	All changes are directly related to the ui_LifebarOnlyDamaged feature implementation; no unrelated modifications are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The pull request description is comprehensive and well-structured, covering all essential aspects: a clear summary of the feature, behavior explanation, technical implementation details, file changes, and a detailed test plan.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@section/LifebarFilter.cpp`:
- Around line 14-17: Update the comment block documenting HP offsets to match
the actual implementation and include/moho.h: change the mapped offsets so
UserEntity_base.mVarData @ +0x4C plus SSTIEntityVariableData.mHealth @ +0x18 ->
UserEntity +0x68, and SSTIEntityVariableData.mMaxHealth @ +0x1C -> UserEntity
+0x6C (this aligns with the reads in LifebarFilter where the code uses +0x68 and
+0x6C for health and max health). Mention include/moho.h as the corroborating
source and remove the incorrect +0x64/+0x68 mapping from the comment.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a9adef0b-ccff-41ab-abdf-1f8975dcf956

📥 Commits

Reviewing files that changed from the base of the PR and between 8da86fe and eaa8dd9.

📒 Files selected for processing (4)

• Info.txt
• changelog.md
• hooks/LifebarFilter.hook
• section/LifebarFilter.cpp

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Fix the documented HP offsets.

These comments say mHealth / mMaxHealth resolve to UserEntity +0x64 / +0x68, but the implementation reads +0x68 / +0x6C at Lines 76-77, which also matches include/moho.h. Please correct the comment so future maintenance does not “fix” the asm to the wrong fields.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@section/LifebarFilter.cpp` around lines 14 - 17, Update the comment block
documenting HP offsets to match the actual implementation and include/moho.h:
change the mapped offsets so UserEntity_base.mVarData @ +0x4C plus
SSTIEntityVariableData.mHealth @ +0x18 -> UserEntity +0x68, and
SSTIEntityVariableData.mMaxHealth @ +0x1C -> UserEntity +0x6C (this aligns with
the reads in LifebarFilter where the code uses +0x68 and +0x6C for health and
max health). Mention include/moho.h as the corroborating source and remove the
incorrect +0x64/+0x68 mapping from the comment.